A video gamer killed two people and wounded several others on Sunday when he opened fire with a handgun at a tournament that was being streamed online from a restaurant in Jacksonville, Fla., police said.

Jacksonville Sheriff Mike Williams named the shooter as David Katz, 24, of Baltimore and said he was in town for the competition. He declined to comment on what led to the third major mass shooting to hit Florida in the last two years.

Williams said Katz killed himself after the shooting and that his body was found along with those of his two victims. Williams said nine people were wounded by gunfire and at least two others were injured while fleeing the scene.

Dozens of ambulances and police cars flooded into Jacksonville Landing, a waterfront dining, entertainment and shopping site in the city's downtown, after several shots rang out on a sunny Sunday afternoon.

The shooting took place during a regional qualifier for the Madden 19 online football game tournament at the GLHF Game Bar inside a Chicago Pizza restaurant, according to the venue's website.

The tournament was being livestreamed when several shots rang out, according to video of the stream shared on social media. In the video, players can be seen reacting to the gunfire and cries can be heard before the footage cuts off.

GRAPHIC CONTENT: Gunfire heard at Florida video game tournament

GRAPHIC CONTENT: Players at a video game tournament heard reacting as a shooting unfolds 0:31

Taylor Poindexter and her boyfriend, Marquis Williams, had travelled from Chicago to attend the tournament, and they fled when the gunfire erupted. She said she saw the gunman take aim at people.

"We did see him, two hands on the gun, walking back, just popping rounds," Poindexter told reporters. "I was scared for my life and my boyfriend's."

Gamer Chris "Dubby" McFarland, was hospitalized after a bullet grazed his head. "I feel fine, just a scratch on my head. Traumatized and devastated," he wrote on Twitter.

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Another Twitter user, Drini Gjoka, said he was in the tournament and was shot in the thumb.

"Worst day of my life," Gjoka wrote on Twitter. "I will never take anything for granted ever again. Life can be cut short in a second."

The latest rampage occurred amid a debate over U.S. gun laws that was given fresh impetus by the massacre in February of 17 people at a high school in Parkland, Fla.

Two years ago, a gunman killed 49 people at the Pulse nightclub in Orlando, Fla.

The sheriff's office said many people were transported to hospital and its deputies were finding many people hiding in locked areas at The Landing.

Six victims were taken to Jacksonville's UF Health Hospital, five of them in stable condition and one in serious condition, hospital staff said.

The shooting took place during a regional qualifier for the Madden 19 online football game tournament at the GLHF Game Bar inside a Chicago Pizza restaurant, according to the venue's website. (Will Dickey/The Florida Times-Union/Associated Press)

A spokesperson for Jacksonville's Memorial Hospital said it was treating three victims, all of whom were in stable condition.

Jacksonville, on Florida's Atlantic Coast, is about 56 kilometres south of the Georgia state line.

Florida Gov. Rick Scott, a Republican who is challenging longtime Democratic Sen. Bill Nelson in November's election, said he had offered to provide local authorities with any state resources they might need.

"Word of another tragic mass shooting in our state brings shock and outrage," Nelson said on Twitter.

Florida highway patrol officers block the entrance to the Main Street Bridge near the scene of a mass shooting at Jacksonville Landing. (John Raoux/Associated Press)

Florida Sen. Marco Rubio said both the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives were co-ordinating with local authorities.

President Donald Trump has been briefed and is monitoring the situation in Jacksonville, the White House said.

Reacting to news of the shooting during the tournament involving its video game, Madden 19 maker Electronic Arts Inc. said it was working with authorities to gather facts.

"This is a horrible situation, and our deepest sympathies go out to all involved," the company said on Twitter.